aquaria: their present, past, and future. 255 
pouring it, and the motion of it as it trickled onwards to the 
sea, purified it, because such an act was an unconscious imitation 
of what nature does. Had Sir John but thought of the merely 
vehicular character of water, and of its incapability of being 
decomposed save by a very slow and expensive process, he 
would at once have seen that the minutely disseminated 
mussel flesh and its juices in the water made that water unfit 
to support life, only temporarily. It was not the water itself 
that was not fit ; it was only something in the water that was 
wrong, and if that something were removed the water would be 
left as good as ever. If, therefore, instead of sending it back 
into the sea by a long road, and then going to the im- 
mense pains to dip it back again, he had poured it into a large 
receptacle in his own house, such receptacle or reservoir being 
many times larger than the aggregate contents of all his glass 
jars, he would have found that in a short time he would have 
possessed a source of supply for the jars quite as good as the 
ocean provided. Had he, in addition, placed his reservoir in a 
cool cellar, and had a pipe connecting it with the study to which 
Miss Dalyell has incidentally alluded, with a funnel at the upper 
end of the pipe, in which was placed a piece of straining-cloth 
or a small hair-sieve, to arrest the coarser pieces of decaying 
organisms, and if he had poured the water he had used into 
this funnel, the arrangement would have been still better. Yet 
better would it have been had he possessed another pipe leading 
upwards from the reservoir, through which he could pump up 
the sea-water as he wanted it. Best of all would have been 
some form of incessantly-working machinery, by means of 
which the water would be always coming up day and night 
from this large and cool reservoir into the experimental glasses, 
for then they would have been constantly kept at an even temper- 
ature and in a state of constant aeration. This would have done 
away with the necessity of the everlasting wiping and washing 
of the glasses : and, they being thus left alone, and in a certain 
amount of daylight, vegetation would soon have appeared in 
them, stimulated by the action of that light, without having 
been visibly introduced, but present everywhere in the seeds or 
spores of plants, merely waiting to be developed. Such an 
arrangement, indeed, would have been precisely that of the 
best modern aquaria as now made, in which the water is so 
continually and abundantly aerated by ceaselessly moving 
machinery, that impurities have no time to accumulate, but 
are oxygenated and dissipated as quickly as they form. In 
the Brighton and Havre public aquaria, the old and inter- 
mittent system used by Dalyell has been reverted to, and of 
course with ill results, as the water freshly obtained from the 
sea is turbid when seen in large masses, and is unhealthy for 
